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Gilman JM, Schmitt WA, Wheeler G, et al. Variation in Cannabinoid Metabolites Present in the Urine of Adults Using Medical Cannabis Products in Massachusetts. JAMA Netw Open. 2021;4(4):e215490. doi:10.1001/jamanetworkopen.2021.5490
A growing market of medical cannabis products claim to have specific Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) content, but regulation of THC and CBD content is inconsistent across states and generally weak.1 To examine the association between medical cannabis product use and exposure to THC and CBD, we quantified levels of THC, CBD, and their metabolites in urine of participants in a clinical trial (ClinicalTrials.gov identifier NCT03224468) of medical cannabis in Massachusetts.
This cohort study was approved by the Partners Human Research Committee. All participants provided written informed consent. This study follows the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline.
Adults (aged 18-65 years) with a desire to use cannabis for depression, pain, or insomnia were recruited through advertising and were assessed at baseline and 2, 4, 12, 24, and 48 weeks after initiating cannabis. The study took place between June 2017 and August 2020. At each visit, participants provided a urine sample, reported recency of cannabis use, and reported whether their primary products were THC-dominant, CBD-dominant, or approximately equal CBD and THC. Samples collected during visits in which participants reported using products from licensed dispensaries within the prior 48 hours and at least 3 to 4 days per week since the previous visit were analyzed using high-performance liquid chromatography with tandem mass spectrometry.2
We ran separate models for THC and CBD metabolites using Kendall rank correlations for ordinal variables and logistic regressions for nominal variables, using R statistical software version 4.0 (R Project for Statistical Computing). All tests and 95% CIs were 2-sided, and significance was defined as P < .05. For logistic regressions, we performed a Wald test. Data analysis was performed from September 2020 to February 2021.
Ninety-seven participants (mean [SD] age, 39.6 [14.74] years; 65 women [67.01%]) provided 256 urine samples meeting the criteria for analysis. Participants were light users at baseline (53% used less than monthly). After baseline, 39% to 47% used 3 to 4 days per week, 15% to 20% used 5 to 6 days per week, and 29% to 45% used daily.
At least 1 cannabis metabolite was detected in 220 samples (85.9%) (Table 1). Among participants who reported using CBD-dominant or equal CBD-THC products, there was no detectable CBD metabolite in 10 samples (30.3%) and 20 samples (37.0%), respectively (Table 2). THC was detected in 26 samples (78.8%) from participants reporting use of CBD-dominant products. Among samples from participants reporting THC-dominant or equal CBD-THC products, no THC metabolites were present in 13 samples (10.9%) and 19 samples (35.2%), respectively.
Although vaping was the most common method of administration, 27 samples (19.7%) from participants who reported vaping contained no measurable cannabinoid whatsoever. CBD metabolites were more likely to be detected in participants who used oral than vaped (odds ratio [OR], 3.01; 95% CI, 1.58-5.74; P < .001) or smoked (OR, 2.99; 95% CI, 1.38-6.47; P = .005) products. THC metabolites were more likely to be detected in participants who used oral (OR, 3.56; 95% CI, 1.42-8.96; P = .007) and smoked (OR, 3.42; 95% CI, 1.26-9.27; P = .02) products than in vaped products.
Among adults using medical cannabis frequently and recently, THC and CBD metabolite concentrations in urine often differed from expected exposure. Approximately one-third of samples from people reporting using CBD-dominant products contained no measurable CBD metabolite. Nearly 1 in 5 samples from those using vaped cannabis contained no detectable cannabinoids. There were no dose-metabolite associations for vaped products. This may indicate that vaping devices may not heat cannabis products appropriately, and US Food and Drug Administration–approved devices may deliver more consistent cannabinoid exposure. Product and delivery method variability present challenges to assessing the efficacy and safety of medical cannabis.
Methodological limitations of this study include participant-determined doses, possible errors in self-report, no analysis of the cannabis products themselves, and individual differences in rate of absorption and metabolism. Products were purchased in Greater Boston dispensaries, so results may not generalize to regions with different regulations.
The findings of this cohort study are consistent with those of a study1 of cannabis products purchased in California and Washington, in which more than one-half of products were incorrectly labeled. These findings indicate that adults using medical cannabis products may have incomplete or incorrect information regarding expected cannabinoid exposure from these purchased products, impeding informed patient choice and investigation of pharmacologic and therapeutic properties of cannabis products.
Accepted for Publication: February 21, 2021.
Published: April 12, 2021. doi:10.1001/jamanetworkopen.2021.5490
Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2021 Gilman JM et al. JAMA Network Open.
Corresponding Author: Jodi M. Gilman, PhD, Center for Addiction Medicine, Department of Psychiatry, Massachusetts General Hospital, 101 Merrimac St, Ste 320, Boston, MA 02114 (firstname.lastname@example.org).
Author Contributions: Dr Gilman had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Concept and design: Gilman, Schuster, Evins.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Gilman.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Gilman, Schmitt, Sempio.
Obtained funding: Gilman, Evins.
Administrative, technical, or material support: Gilman, Schmitt, Wheeler, Klawitter.
Supervision: Gilman, Schuster, Evins.
Conflict of Interest Disclosures: Drs Gilman and Evins reported having a patent pending (WO 2018/027151) and being cofounders of Brain Solutions, LLC. Dr Schuster reported receiving personal fees from the Massachusetts Department of Public Health and the University of Connecticut outside the submitted work. Dr Sempio reported receiving grants from Massachusetts General Hospital during the conduct of the study. Dr Evins reported receiving grants from the National Institutes of Health and Charles River Analytics during the conduct of the study, personal fees from Pfizer and Karuna Pharmaceuticals, and serving as chair of a data safety monitoring board for a trial. No other disclosures were reported.
Funding/Support: This work was supported by grant R01DA042043 from the National Institute on Drug Abuse, National Institutes of Health.
Role of the Funder/Sponsor: The funder had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
Additional Contributions: Kevin Potter, PhD (Massachusetts General Hospital), assisted with statistical analyses; he was not compensated for this work beyond his normal salary.